I'll never forget my honeymoon. It was the first time I had missed the start of the fishing season since I was 12 years old.

Even then, I might have got away with it if I hadn't written 'START OF FISHING SEASON' against 16 June. I should have put 'HOSPITAL SCAN FOR CANCEROUS GROWTH' or 'URGENT MEETING WITH LOCAL MP'. But it had become a ritual, one of those essential dates like your mother's birthday (miss it at your peril) that you write in every new diary.

And even today, though I am older, greyer, fatter and busier; though the cheap Lett's diary has been replaced by an executive Filofax, that habitual legend still nestles, between a flurry of meetings and a summer party. Nothing, of course, was arranged for yesterday. It was the start of the season, an occasion more holy than a cardinals' party at the Vatican.

This odd devotion to the pursuit of the inedible (coarse fish such as roach, bream, tench and chub are generally poor eating) is shared by hundreds of thousands. In many areas of London, departmental managers and shop-floor foremen will have puzzled over the sudden sharp rise in absenteeism (always assuming they were not skiving themselves).

The ceremony of going fishing on 16 June, weekend or weekday, rain or shine, is one no serious angler will deny.

A curious thing, this ritual celebration of a new fishing season. Primitive as a fertility dance, the June bug has precious little to do with fish concluding their sexual affairs for another year. (Fish have not learnt about calendars yet, so they spawn when the water is warm enough, rather than arranging it conveniently during the last week of May). It doesn't even have much to do with catching fish.

Most anglers will capture very little or nothing today, whether they are on an exclusive stretch of the Kennet or public ponds on Hampstead Heath. After all, the fish have not seen a maggot or slice of bread for months. They have become accustomed to more wholesome food such as bloodworm, snails, weed and microscopic water creatures, and will not change diets overnight.

In murky pond or turbid canal, life underwater has been peaceful for months. Suddenly, this tranquility is disturbed by the pounding of wellingtons, the splash of float, the thump and rattle of fishing boxes. Anglers swear darkly that the fish seem to know it is the start of the season. But then, so would you if your neighbours held a raucous party every 16 June.

Appearing on the bankside at some time yesterday will generally be enough to placate St Gudgeon, or whoever the patron of coarse fishing is. But the true devotee will have been casting a line as the last stroke of midnight sounded.

Arriving by 12 o'clock on the fishing day of days is no guarantee of securing your favoured spot. On popular waters such as Clapham Common, it is not unusual to find every spot taken before dusk falls. But the real extremists will have booked their pitch for days, to ensure that nobody can pip them to a particularly fruitful area.

This involves setting up home on the bank. In recent years, huge advances on home comforts have been made. I do not mean mere tents and sleeping bags: many serious fishermen now pack portable generators to run lights and a television. Some even fit carpets to tents. (No Muddy Boots Inside Please.)

Those who achieve this particular level of fanaticism become rather strange. I recall visiting one such person who had been on the bank alone for five days, and heard him talking as I approached. Not wanting to disturb him, I crept up silently and found him in earnest conversation with a spider. Holding intellectual discussions with arachnoids tends to affect more traditional relationships. Such anglers are usually unmarried, divorced or likely to become so shortly.

But even those who just want to welcome the new season by Being There at midnight and packing up as dawn breaks find it hard to persuade loved ones to share the magic.

Rare indeed is the woman who will spend more than one opening night on the bank. They may enjoy the champagne moment (often literally) but mosquitoes, bats and things that make spooky noises discourage all but the most besotted female. One opening session, my brother had a rat run across his face. (He is the only person I have ever seen leap in the air from a prone position.) Such delights are rarely a woman's idea of a good time.

Not that the real fisher needs companionship on 16 June anyway. (Research shows that 69 per cent of anglers go fishing to get away from it all.) Picture this. You're on the bank alone, in pure silence, as dawn breaks and the mist rises off the water. A zillion-watt light bulb switches on over the horizon, promising a perfect June day. Nature is waiting to see what happens next. It's like the opening of a film about creation (production, dubbing, editing and direction by God). Suddenly a huge, unidentified fish swirls near your float. The tension builds inside you. Is that giant nosing towards your bait?

Of course it isn't. The fish is far too smart for that. But if you ask why I and thousands of Londoners were sitting by lake and pond, river, stream and canal at 4am yesterday, I would say it is because the renewal of faith in nature, beauty, fishing and much more is contained in the essence of it all, that perfect moment. If it exists, it will be there on opening day.

Then again, perhaps they just wanted to get away from the wife and kids, or have a day off work.